In recent years, the high-frequency microwave epitaxy chip is used in wide range, for example, mobile communication, global position system, wireless network etc. Therefore, the high-frequency element development has become the irresistible tide of the day. Specifically, the compound semiconductor epitaxial fabrication is one of the most development technologies.
There are three main types of the compound semiconductor epitaxial fabrication: Large Electron-Positron (LEP), Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD).
The Large Electron-Positron (LEP), which is very traditional and easy manner, is applied in manufacturing the light emitting diode (LED). However, it is difficult to use LEP to manufacture the epitaxy layer with high doping concentration or the thin thickness.
The Molecular beam epitaxy (MBE), which is generated by the Physical optics method. The MBE is a successful generation technology and the production yield rate of MBE is higher. However, the cost of MBE is also higher.
The Metal-Organic Chemical Vapor Deposition (MOCVD) which has various chemical change and great technology difficult. However, the manufacture cost of MOCVD is lower and the production of the MOCVD is higher than the MBE. Moreover, the element manufactured by MOCVD has small size, high power, and the element is widely used in the mobile phone, for example, Pseudomorphic High Electron Mobility Transistor (PHMET), High Electron Mobility Transistor (HEMT), Metamorphic High Electron Mobility Transistor (MHEMT), etc.
Generally, the Metamorphic High Electron Mobility Transistor (MHEMT) is composed of InAlAs buffer layer. InAlAs spacer layer. InAlAs channel layer, InAlAs capping layer, and the MHEMT is grew on the substrate with InP or GaAs. However, the substrate with InP or GaAs is very expensive and has bad performance of mechanical, and it will cause that MHEMT is not easy to grow on the larger substrate and is also rapidly increasing in prices of cost.
In general technology, it combines the Si substrate and the III-V Compound semiconductor, and the SixGe1-x substrate is used to be the buffer layer, and the Ge film is grown on the Si substrate. Specifically, the SixGe1-x substrate compositing of the graded Ge is used in wide ranges. However, the thickness of the SixGe1-x substrate will achieve the tens mm. Therefore, the manufacture cost of the SixGe1-x substrate is higher and the MHEMT manufactured also has the deep thickness, and the mismatch and bug are also easy generated in growing of the GaAs.
Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the disclosure, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description.